class Solution
{
public:
    bool containsNearbyDuplicate(vector<int> &nums, int k)
    {
        unordered_map<int, int> hash;
        for (int i = 0; i < nums.size(); i++)
        {
            int tmp = nums[i];
            if (hash.count(tmp) && (i - hash[tmp] <= k))
                return true;
            hash[nums[i]] = i;
        }
        return false;
    }
};
